Method of ascertaining the presence of petroleum deposits in earth formations



METHOD OF ASCERTAININ G THE PRESENEE F PETROLEUM DEPOSITS IN FORMA- TIONS John W. Graham, Bellaire, andJoseph S. Osoba, Houston, Tex., assignors, by mesne assignments, to Jersey Production Research Company, Tulsa, Okla., a corporation of Delaware No Drawing. Filed Mar. 1 1957,. Ser. No. 643,255;

9 Claims. (Cl. 250-71) This invention relates to. well logging methods and more particularly to methods for testing for thepresence of petroleum deposits in the various strata of the earth.

During the course of drilling a borehole in the earth in the search of petroleum deposits, it is necessary to periodically test the nature of the strata penetrated by the borehole to ascertain whether or not petroleum deposits may exist therein in commercially desirable quantities. It is particularly necessary to make such tests when the petroleum deposits do not make their presence known by a self-sustained rise to the earths surface. In the past it has been common practice to make various types of logs of-the characteristics of the borehole, such as electric logs, radio activity logs, acoustic impedancelogs and the like. While such logs are quite valuable for the purpose of obtaining geologic information, manifestly they require that. drilling operations be interrupted, and further require the use of bulky, complicated and rather expensive equipment if accurate results are to be obtained,

Accordingly, it is one object of the invention to pro-. vide an improved method of continuously. logging a borehole wherein drilling operations may continue unimpeded.

Another object is to provide a method for logging a borehole making use of simple, relatively inexpensive apparatus.

Still another object is to provide a method for logging a borehole that provides for a simple process of detection of petroleum content in the earths layers withoutthe necessity for interpreting complicated logging records.

Other objects and features will become readilyv apparent upon consideration of the following detailed description, thereof.

In accordance with the teachings of the present iuven tion, the presence of crude oil in the earths strata is detected or ascertained by operations on the very small rock chips carried to the earths surface by. drilling mud during drilling operations. According to one aspect of this invention, the presence of hydrocarbons is detected by contacting the surface of a rock chip with a surface: active agent, of the type that causes preferential wetting of the surface by hydrocarbons present therein (so-called reverse-Wetting agents) and subjecting the chips to ultra-violet light. By comparing the relative fluorescence of the surface of the chip before and after the contacting operation, a positve indicationof' the presence of hydrocarbons may be obtained.

It is preferable to obtain two rock chips froma small section of the earths stratum being penetrated; by the drilling bit. For this purpose, it is mostdesirable to obtain a chip large enough to yield two chips of approximately the same size for the operation to be described below; however if convenient, it may be feasible to take two chips that are brought to the surface by the drilling mud at approximately the same time, this indicating they were severed from the earth by the drilling bit wit-hin;t he same stratum of the earth and within the same general region or section thereof. The surface of only one of the chips is contacted with the reverse-Wetting agent, and di- 2, rect comparison of relative fluorescence is made under ultra-violet light.

The surface-active or reverse-wetting agent may be in an. aqueous solution or the pure agent itself may be used;

If'the agent is in solution, it is desirable that a brine solution be used to avoid reduction of the permeability of the chip brought about by fresh water contacting the clays therein. Preferably the salt concentration should not exceed about 10% salt; at that concentration of' salt, most of the reverse wetting agents will become. substantially insoluble.

The surface-active (or reverse-wetting) agent, maybe any of a number of types known to the priorart., Surface-active agents that have been found to be effective include certain of the amine salts and certain quaternary ammonium salts. The organic amine base used for the preparation, of the amine salts is selected from primary, secondary and tertiary. alkyl, aryl, and aralkyl amines which contain only one nitrogen atom and no other combined atoms other than carbon, hydrogen and'nitrogen in the molecule and in which the ratio of combined atomic weights of carbon and hydrogen atoms for each basic nitrogen atom in the molecule is in the range, from 125 to 300, and which have dissociation constants (for hydronyl ion in aqueous solution of the base) within the limits of 1 1Q- to l 10- The acids to be reacted with the amine bases may be acetic, hydrochloric, sulphuric, formic, propionic, citric, lactic, nitric, or'phosphoric. When the water in the drilling fluid is essen tiallyfree of salt, it is preferable to, use organic bases near-the upper limit of the above-specified range of ratios of carbonandhydrogen to basic nitrogen. As the salinity of the water increases, the basic materials will decrease in solubility, so it is desirable to use organic bases. near the lower end of the above-recited range.

Specific examples of surface-active agents suitable for use with thisinvention are set forth below:

A very effective reverse-wetting solution has been foundto be 2% Arrnac CD-SO in a brine solution containing about 5000 partsper million of salt. Armac CD- SO-is a mixtureof alkyl-amine acetate from C to C predominately C and G with a minor amount of C with-one point of unsaturation. More specifically, the composition is-8% octyl, 9% decyl, 47% dodecyl, 18% tetradecyl, 8% hexadecyl, and 5% octadecyl amine acetate. Other. reverse Wetting agents that may be utilized are: octadecyl amine acetate; cetyl dimethyl amine acetate; Tetrosan, a cationic surfactant sold by'Onyx Oil and. Chemical ('20., Jersey City, NJ Acetate of Primene JM-IILa mixture of primary amines with branched chains containing from 15 to 20 carbon atoms, sold by Rohm and, Haas; Arquad C2 which is dicoco dimethyl ammonium chloride prepared from coconut oil; amine acetate prepared from Primene 81R, which is a mixture of primaryamines containing branched chains of 12 to 15 carbon atoms, sold by Rohm and Haas; alkyl tolylmethyl trimethyl ammonium chloride; lauryl benzyl dimethyl ammoniumchloride; bis quartcrnary salts such as the reac,- tion product of 2 octyl benzyl chloride with his dimethyl amino butylene, and the reaction product of nonyl benzyl chloride with bis dimethyl amino butene; diisobutyl cresoxyethyl dimethyl benzyl ammonium chloride; and diisobutyl phenoxyethoxy ethyl dimethyl benzene ammonihence increase visability of chip surface.

Both of the chips are now placed side by side under an ultra-violet lamp and the relative fluorescence of the chips produced by the ultra-violet rays is noted. If a small amount of residual crude oil or other fluorescing minerals is present in the interstices of the chips, then the chips that was not subjected to the reverse wetting agent will show spotty or very dim fluorescence, or perhaps no fluorescence at all if oil has been washed from the surface of the chip during its travel up the borehole. The chip that has been subjected to the reverse wetting agent will fluoresce brightly if residual crude oil is present'in the interstices thereof inasmuch as the action of the altered capillary forces will bring the oil within the chip to the surface thereof. This rapid change in surface fluorescence is indicative of the presence of petroleum deposits in the particular subsurface stratum being penetrated by the drilling bit.

It should be noted further that certain of the reverse wetting agents specified above are themselves fluorescent. When these reverse wetting agents are utilized, they must be used in concentrations such that their fluorescence will not be confused with the fluorescence of the oil.

In carrying out the method of this invention, it is mandatory that drilling muds be utilized which contain no fluorescent materials. The exclusion of fluorescent materials from the drilling mud is an absolute requisite inasmuch as faulty indications of petroleum deposits will almost inevitably result where such exclusion is not made.

Although the invention as disclosed in the preceding specification is preferred, modifications will be apparent to those skilled in the art which do not depart from the broadest aspects of the scope of the invention.

What is claimed is: V

1. A method for determining the presence of petroleum in an earth formation penetrated by a borehole comprising the following steps: while drilling said borehole, using drilling fluid from which fluorescent materials have been excluded; obtaining a sample of said earth formation and dividing it into two pieces; contacting the surface of one of said samples with a non-fluorescent solution containing a cationic surface active agent which causes preferential wetting of said surface by petroleum present therein; exposing said samples to ultra-violet light; and comparing the relative fluorescence of the surfaces of said samples.

2. A method for determining the presence of petroleum in an earth formation penetrated by a borehole comprising the following steps: while drilling said borehole, using drilling fluid from which fluorescent materials have been excluded; obtaining two samples of said earth formation from a given portion of said earth formation; washing one of said samples in a brine solution containing up to about salt; washing the other sample in a brine solution additionally containing a cationic surface-active agent which causes preferential wetting of said surface by petroleum present therein; exposing said samples to ultra-violet light; and comparing the relative fluorescence of the surfaces of said samples.

3. A method for determining the presence of petroleum in an earth formation penetrated by a borehole comprising the following steps: while drilling said borehole, using drilling fluid from which fluorescent materials have been excludedTobtaining two samples of said earth formation from a given portion of said earth formation; contacting the surface of one of said samples with a nonfluorescent solution containing a cationic surface-active agent which causes preferential wetting of said surface by petroleum present therein; exposing said samples to ultra-violet light; and comparing the relative fluorescence of the surfaces of said samples.

4. A method for determining the presence of petroleum in an earth formation penetrated by a borehole comprising the following steps: while drilling said borehole, using drilling fluid from which fluorescent materials have been excluded; obtaining a sample of said earth forma- 4 tion and dividing it into two pieces; contacting the surface of one of said samples with a non-fluorescent fluid including a cationic surface-active agent which causes preferential wetting of said surface by petroleum present therein; exposing said samples to ultra-violet light; and comparing the relative fluorescence of the surfaces of said samples. 7

5. A method for determining the presence of petroleum in an earth formation penetrated by a borehole comprising the following steps: while drilling said borehole, using drilling fluid from which fluorescent materials have been excluded; obtaining two samples of said earth formation from a given portion of said earth formation; washing one of said samples in a brine solution containing to about 10% salt; washing the other sample in a non-fluorescent brine fluid additionally including a cationic surface-active agent which causes preferential wetting of said surface by petroleum present therein; exposing said samples to ultra-violet light; and comparing the relative fluorescence of the surfaces of said samples.

6. A method for determining the presence of petroleum in an earth formation penetrated by a borehole comprising the following steps; while drilling said borehole, using drilling fluid from which fluorescent materials have been excluded; obtaining two samples of said earth formation from a given portion of said earth formation; contacting the surface of one of said samples with a non-fluorescent fluid including .a cationic surface active agent which causes preferential wetting of said surface by petroleum present therein; exposing said samples to ultra-violet light; and comparing the relative fluoresence of the surfaces of said samples.

7. A method for determining the presence of petroleum in an earth formation penetrated by a borehole comprising the following steps: while drilling said borehole, using drilling fluid from which fluorescent materials have been excluded; obtaining a sample of said earth formation; contacting the surface of said sample with acationic surfaceactive agent which causes preferential wetting of said surface by petroleum present therein; subjecting the sample to ultraviolet light; and determining whether or not a change in fluoresence of said sample is brought about by the step of contacting the surface of said sample with said surface-active agent.

8. A method for determining the presence of petroleum in an earth formation penetrated by a borehole comprising the following steps: while drilling said borehole, using drilling fluid from which fluorescent materials have been excluded; obtaining two samples of said earth formation from a given portion of said earth formation; contacting the surface of one of said samples with a nonfluorescent fluid including a surface-active agent which causes preferential wetting of said surface by petroleum present therein, said surface-active agent being an amine salt formed by reacting an acid selected from the group consisting of acetic, hydrochloric, sulphuric, formic, propionic, citric, lactic, nitric, and phosphoric acids with an amine base selected from the group consisting of primary, secondary and tertiary alkyl, aryl, and aralkyl amines which contain only one nitrogen atom and no other combined atoms other than carbon, hydrogen and nitrogen in the molecule and in which the ratio of combined atomic weights of carbon and hydrogen atoms for each basic nitrogen atom in the molecule is in the range from to 300, and which have dissociation constants (for hydronyl ion in aqueous solution of the base) within the limits of 1x10 to 1 10- exposing said samples to ultraviolet light; and comparing the relative fluorescence of the surface of said samples.

9. A method as in claim 1 wherein the amine salt is a mixture of 8% octyl, 9% decyl, 47% dodecyl, 18% tetradecyl, 8% hexadecyl, and 5% octadecyl amine acetate.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Smith July 9, 1940 Hayward Aug. 27, 1940 5 Hayward Sept. 10, 1940 Campbell Jan. 7, 1941 Blau Jan. 13, 1942 6 Campbell Feb. 16, 1943 Boeke Nov. 28, 1944 Rand Feb. 10, 1948 Stevens et a1. Oct. 19, 1948 Ten Brink Aug. 12, 1952 Strange et a1. Aug. 24, 1954 Crass et a1. Apr. 3, 1956 Coggeshall et a1. Oct. 16, 1956 

1. A METHOD FOR DETERMINING THE PRESENCE OF PETROLEUM IN AN EARTH FORMATION PENETRATED BY A BOREHOLE COMPRISING THE FOLLOWING STEPS: WHILE DRILLING SAID BOREHOLE, USING DRILLING FLUID FROM WHICH FLUORESCENT MATERIALS HAVE BEEN EXCLUDED, OBTAINING A SAMPLE OF SAID EARTH FORMATION AND DIVIDING IT INTO TWO PIECES, CONTACTING THE SURFACE OF ONE OF SAID SAMPLES WITH A NON-FLUORESCENT SOLUTION CONTAINING A CATIONIC SURFACE ACTIVE AGENT WHICH CAUSES PREFERENTIAL WETTING OF SAID SURFACE BY PETROLEUM PRESENT THEREIN, EXPOSING SAID SAMPLES TO ULTRA-VIOLET LIGHT, AND COMPARING THE RELATIVE FLUORESCENCE OF THE SURFACES OF SAID SAMPLES. 